We propose to determine the sequence organization of the proviruses of the cat viruses, RD-114 and FeLV, and of the baboon endogenous virus (BEV), in the natural host genomes and in heterologous infected cells using recombinant DNA methods. Cloned proviruses will be characterized by standard gene mapping methods, including electron microscopy and restriction endonuclease mapping. Particular attention will be paid to the difference in sequence organization of infectious and non-infectious proviral DNA sequences.